Magnesium alloys and method of making the same



Oct. 20, 1953 H. E. DUNN ETAL 2,656,269

MAGNESIUM ALLOYS AND METHOD OF MAKING THE SAME Filed March-'8, 1951 3 Sheets-Sheet 1 Temperature 0 O l0 Cu I00 90 20 3O 4O 5O 6O 7O 8O 90 I00 Si 80 7O 6O 5O 4O 3O 20 .IO 0

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INVENTORS Ho/berl E Dunn y .Jerome Strauss y M6 w THE/R ATTORNEYS Oct- 20, 1953 E, DUNN ET AL 2,656,269

MAGNESIUM ALLOYS AND METHOD OF MAKING THE SAME Filed March' a, 1951 s Sheets-Sheet 2 I Cu ,9 emmladwa Mg I00 IN VEN TORS Ho/berf A. Dunn y Jerome Strayss Oct. 20, 1953 DUNN ET AL 2,656,269

MAGNESIUM ALLOYS AND METHOD OF MAKING THE SAME Filed March 8, 1951 3 Sheets-Sheet 5 O 0. ON 0m 0w On 00 on 0m 0m 00- n a 09 om 8 E 8 on 3 on 8 2 o A o3 ",9 emuuedwa INVENTORS Ho/berl E Dunn By Jerome $Irauss THE/R ATTORNEYS Patented Oct. 20, 1953 l YPIUNITEo MAGNESIUM ALLOYS AND METHOD OF MAKING THE SAME Holbert Dunn, .Crafton, Pa., and Jerome Strauss, New York, N. Y.,' assignors to Vanadium Corporation of America, New York, N. Y., a corporation of Delaware Application March 8, 1951, Serial No. 214,462

13 Claims.

This invention relates to magnesium alloys and to a method of making the same. More specifically, the alloys contain magnesium, copper and silicon, or magnesium, copper, silicon and iron. These; alloys are useful in the treatment of cast iron or steel. The final alloys suitable for treating cast iron or steel are generally referred to herein as treatment alloys" in order to distinguish them from other preliminary alloys used in making the treatment alloys,

The compositions of typical treatment alloys are given in the following Table I, it. being understood that these are merely typical'examples andthat the proportionsof. the ingredients can be varied quite widely to suit particular conditions. 7

TABLE I Percent Mg 6 6 9 9 9 13 8 Percent Cu 6 7 l2 l0 l0 9 13 Percent Si 34 20 34 24 21 30 27 Percent, Fe 54 67 45 57 60 48 62 Ratio Ou/Mg 1. O 1. 16 1. 33 1. 1 .1. 1 O. 7 1. 6 Ratio Si/Mg- 5. 67 3. 3 3. 8 2. 67 2. 3 2.3 3. 4

The method heretofore employed in making these treatment alloys has been to melt a mixture of magnesium metal, copper scrap, silicon metal, and iron punchings and/or ferrosilicon in a covered fuel-fired graphite crucible. Direct melting of the metals in this manner results in a considerable loss amounting in some cases to as much as 50% of the magnesium by volatilization and oxidation. The melting points of the metals involved are as shown in the following Table II:

TABLE II Melting Boiling Point, 0 Point, o.

Since the melting points of the treatment alloys range in general from 1200 to 1280 C., it is readily seen why there is a considerable loss of magnesium in forming the treatment alloys by the direct melting of the metal-s as heretofore carried out. We have discovered a method whereby this high loss of magnesium can be for the most part and in some cases entirely avoided in forming the treatment alloys and have produced alloys not heretofore known.

In the accompanying drawings:

Figure 1 is a phase diagram of copper-silicon alloys; 7

Figure 2 is a phase diagram 'of copper-magnesium alloys; and

Figure 3 is a phase diagram of iron-silicon alloys.

In carrying out our preferred method we form a copper-silicon alloy, this alloy being generally referred to hereinafter as alloy A. This copper-silicon alloy A preferably contains copper and silicon in the eutectic proportions of substantially 83.5% copper and 16.5% silicon, which has a melting point of 802 C. We form a magnesium-copper alloy which is hereinafter generally designated as alloy B. This magnesiumcopper alloy B preferably contains magnesium and copper in substantially the eutectic proportions ,of 69.3% magnesium and 30.7% copper having a melting point of 485 C. The eutectic proportions for alloy A and alloy B are preferred, but, of course, other than the eutectic proportions of the metals can be employed in accordance with the principles herein disclosed.

Having formed the copper-silicon alloy A and the magnesium-copper alloy B, we alloy having a melting point lower than the melting point of either copper or silicon. Accordingly, magnesium can be alloyed with alloy A at a lower temperature than it could be alloyed with either copper or silicon alone or incorporated into a treatment alloy by the prior art method. In making the magnesium-copper alloy B we provide a magnesium and copper containing alloy having a melting point lower than the melting point of either copper or magnesium. Accordingly, we can alloy solid alloy A with molten alloy B at a lower temperature initially than we could alloy alloy A with molten magnesium alone and we thereby reduce losses of magnesium by volatilization. In addition, the boiling point ;of the magnesium-copper alloy B is higher than the boiling point of magnesium alone so that alloy A and alloy B can be alloyed together without any substantial loss of magnesium. Of course, the vapor pressure of magnesium alone or when in these magnesium containing master alloys is appreciable at temperatures below its boiling point so that there is a tendency to volatilize at these lower temperatures. However, experience has shown that such volatilization does not result in losses of commercial significance and hence it is important, as pointed out herein, to give primary con sideration to the boiling point and to avoid closely approaching or exceeding this temperature.

The ternary master alloy of magnesium, cop- ..per and silicon has a higher melting point and a higher boiling point than the melting points and boiling points of either alloy A or alloy .13. Accordingly, the addition of the ternary master alloy .to molten ferrosilicon in forming the treatment alloy results in less loss of magnesium than would be the case were either alic A .or alloy B added to molten ferrosilicon.

Instead of making alloy A by melting silicon metal and copper metal we can replace a part or all of the silicon metal by ferrosilicon, thereby producing an alloy A containing silicon, copper and iron in which the iron preferably is relatively .low in amount. When this siliconcopper-iron containing alloy A is alloyed with .the. magnesium-copper alloy B, it results in .a qu ternary magnesium-copper-silicon-iron alicy which 'is' referred to'hereinafter generally as quaternary master alloy. This quaternary master alloy is then alloyed with ferrosillcon toproduc-e the"treatment alloy.

Theffol1o'wing examples are illustrative of my invention:

Example 1 Step 1.- parts of copper scrap are melted wane parts of crushed silicon metal (these are substantially the eutectic proportions of 83.5%

cbpperand 16.5% silicon). The bath is stirred withan-iron bar and is either granulated and ferred to as "alloy B containing 70% magnesium and 30% copper and having a melting point of about 485 C.

Step 3.-While holding "alloy B molten, the 36 parts of the copper-silicon alloy A are stirred into the 100 parts of the magnesium-copper "alloy B and as soon as it is dissolved the melt is cast into iron chill molds and crushed to 2" by down size to give 136 parts of magnesium-coppersillcon alloy, hereinafter referred to as ternary master alloy and containing 51.4% magnesium, 44.2% copper and 4.4% silicon.

Step 4.-Molten 37 ferrosilicon in an amount of 864 parts by Weight and at a temperature of 1370 to 1430 C. is placed in a ladle and the 136 parts of the ternary master .alloy is added as rapidly as possible to the bath of ferrosilicon, preferably in a period of 5 minutes or less, while puddling the surface with an iron bar to submerge lumps of cold alloy. The melt is 'then cast quickly into an iron chill mold, result- Example 2 Step 1.-This step is exactly the same as step 1 of Example 1.

Step 2.-This step is exactly the same as step 2 of Example 1.

Step 3.This step is :the same as step 3 of Example 1 except that the silicon content of the copper-silicon alloy is increased to 36.5% Si by adding more silicon metal to the molten coppersilicon alloy, and 54.7 parts of the copper-silicon alloy are stirred into-45.3 parts of the step Z-mag- 'nesium-copper alloy, thereby forming a "ternary master alloy containing 31.69% magnesium, 44.57% copper, and 20% silicon, and having a melting point of 1093-C.

Step 4-.-.This step is the same as step 4 of Example 1 except that 236 parts of the ternary master alloy:are added to 764 partsof the molten ferrosilicon containing 37 silicon. Because of the relatively large amount of ternary master alloy added to the-molten ferrosilicon, it is necessary to apply heat in order to dissolve all of it soas to formthe treatment alloy.

In carrying out step 40f this example the .operation is less vigorous thanin carrying out step 40f Example 1 and surfaceburning and flaming 'of volatilized'magnesium .is negligible.

Example;

Step 1.'Instead of using steps 1, '2 and '3 in forming the ternary master alloy as in Example 1, the ternary master alloy is madeby direct melting in a covered graphite crucible 'of' a mixture of magnesium ingot, copper scrap and silicon metal in proportions to produce the "ternary master alloy of Example 1. The recovery of magnesiumb'y this direct melting method is well over and approximately as compared with the approximately recovery-of magnesium .in formingthe ternary master alloy" by the sequential step method of Example 1.

Step 2.-The ternary master alloy is alloyed with ferrosili'con in the same manner as in step 4 of Example 1.

The ternary master alloys," whether produced by the sequential step methods of Examples 1 and 2 or by the direct melting method of Example 3,

6. silicon metal are 'melted to form 7.8 parts of a copper-silicon alloy containing 83.5% copper and 16.5% silicon. The alloy is granulated in water and dried.

5 Step 2.6 arts of ma nesium is melt and may contain from to 55% magnesium, from 7 8 p g ed parts of step 1 alloy (copper-silicon) are fed 12 to 50% copper and from 4 to 60% silicon. The into the molten ma nesium b th th t preferred proportions are from 10 to 40% magfire f th b t b a e emperanesium, from to 50% copper and from 10 to 0 a h increased i the Silicon m tent required for solut1on. When solution is com- The following Table III gives further examples Plete, Parts of ferrosilicon are d to the of various suitable magnesium-copper-silicon 1 bath to duce 18.6 parts of quatern y "ternary master alloys: alloy containing 3 n s m, 3 Cup- TABLE III 1 Composition Ternary Temar Master Alloys Rat) Parts Grad Mast Ternary Parts FeSl, ment Alloy Maister FeS1 Peigren Alloy Pelrlfgnt Pecgnt Perscient Cu/Mg Si/Mg A1 oy 1 (Table I) 1 51.4 44.2 4.4 0.3 0.08 2 51. 4 34. 5 14. 5 0. 7 0. 3 26. 0 74. 0 20. 0 3 I 15.0 35.0 33.0 1 3-. 45. 0 48.0 7. 0 1. 1 0. 2 22. 7 77.3 36. 5 3 1 15.0 35.0 20.0 2 18.7 81.3 35.0 1 4 37. 0 41. 0 22. 0 1. 1 0. 6 17. 1 s2. 0 20.0 2 28.2 71.3 36.5 3 22.0 73.0 32.7 1 5 32.0 36.0 32.0 1.1 1.0 $3 2 33:3 33.3 66.7 20.0 4 24.5 75.5 30.5 1 6 20.0 32.0 30.0 1.1 1. 3. g 37.5 62.5 20.0 4 7 24.0 26.5 43.5 1.1 2.1 22:; g. s 23.0 26.0 I 51.0 1.1 V 2.2 58:8 0 21.0 23.0 56.0 1.1 2.7 g 10 12. 0 25. 0 63. 0 2. 1 5. 3 4s. 0 52. 0 9. 6 1 11 21. 3 14. 4 53. s 0. 7 2. 0 4s. 3 51. 7 10. 4 3

Table III also shows the parts of ternary master alloy and the parts and grade of ferrosilicon which are to be alloyed with the ternary master alloy to produce the various types of treatment alloy referred to in Table I.

Instead of using magnesium-copper-silicon ternary master alloys we may use magnesiumcopper-silicon-iron quaternary master alloys containing a relatively low percentage of iron. These quaternary master alloys may be made by introducing ferrosilicon (preferably 60% silicon grade melting at 1250 C. or silicon grade melting at 1260 G.) into magnesium-copper-silicon "ternary alloys. It may also be made by alloying copper with ferrosilicon to produce a copper-silicon-iron alloy and thereafter alloying such alloy with an alloy of magnesium and copper. Iron does not alloy readily with magnesium. However, a small amount of iron can be introduced into the master alloy and is advantageous in thatit increases'the density of the master alloy while (if limited) keeping the melting point of the master alloy adequately below the boiling point of magnesium. The amount of iron in the master alloys should be less than 20% and the preferred amount is between 3 and 15%.

The following Examples 4 and 5 illustrate the method of making magnesium-copper-siliconiron quaternary master alloys and the making of treatment alloys by alloying the quaternary master alloys with ferrosilicon.

Example 4 Step 1.6.6 parts or copper and 1.2 parts-of 75' per, 22% silicon and 11 iron and having a melting point of 1025 C.

Step 3.Whi1e the step 2 master alloy is held molten, 81.4 parts of molten 20% ferrosilicon carrying as little superheat as possible is poured into it. The resultant treatment alloy contains 6% magnesium, 6.5% copper, 19.4% silicon and 67.2% iron.

Ewample 5 Step 1. parts of copper are mixed with 20 parts of ferrosilicon containing 50% silicon and the mixture is melted, thereby producing alloy A" containing 80% copper, 10% silicon and 10% iron.

Step 2.An alloy containing 70% magnesium and 30% copper is made according to step 2 of Example 1, this alloy being designated alloy B.

Step 3.-While holding 60 parts of alloy B" molten, 40 parts of alloy A are stirred into it 1n the manner described in step 3 of Example 1.

results in a quaternary master alloy contaimng 42% magnesium, 50% copper, 4% silicon and 4 iron. 3

Step 4.16 parts of the quaternary master alloy from step 3 are alloyed with 84 parts ferrosilicon (25% Si) in the manner given in step 4 of Example 1, thereby producing a treatment alloy containing 6% magnesium, 8% copper 22% silicon, and 64% iron. Examples of other magnesium-copper-siliconiron quaternary master alloys which can be used 1n making treatment alloys by alloying the quaternary master alloys are given in the following Table IV:

with ferrosilicon.

T LE Alloy Pefigent Peacllmt" Pcrscient Peii cgnt Cu/Mg SilMg Anny v it) e i 32.0 44.6. 20.0 3.4 1.4 0.63 23. 2;- g; 2 872 2 52.0 55.0 22.0 11.0 22:8 g 3 33.0 36.1 22.7 8.2 1.1 0.69 ggfg g This table also gives the parts of quaternary We claim:

master alloy and the parts and grade of ferrosilicon which are to be alloyed in producing the treatment alloys of the types referred to in Table I.

In place of using straight ferrosilicon fora1lo'y-. ing with the ternary or quaternary master alloys we may use ierrosilicon containing a small amount of copper with advantage. Addition of' copper to ferrosilicon lowers the melting point of the ferrosilicon and thus decreases the. loss of magnesium in alloying the master alloy with the ferrosilicon containing copper. However, the amount of copper allowable in cast: ironor steel is limited and therefore the amount of cop.- per in the treatment alloys is limited... Copper in the master alloy protects-the magnesium by raising the boiling point of the master alloy. Accordingly, a certain amount of coppermusta b'e present in the master alloy and since the total of the copper in the master alloy and the cop:- per in the ferrosilicon is limited, it follows that the amount of copper in the ferrosilicon is lim ited even though it might be advantageous ;to increase this amount because of its effect in lowering the melting point of the ferrosilicon. In order to protect the magnesium of the master alloy weprefer to use. copper inthe master alloy in such amount that therati'oof. the coppertothe magnes umis from 0.4.:[1 to 2:1. With Copper ingthe masterj all'oy. Within the; ratio stated, the amount qf copper: in the ferrosilic'on ordinarilyshouldnot bein excess of 20% of the sil concohtcnt of ..theferrosilicon..

Aspreviously stated, the method heretofore em.- ployed in making magnesium alloys was to melt the magnesium andlalhofrthe other alloying in-' gradients directly, in.v acoyered fuel-fired graphite cruciblejijn order. toguardagainst loss of mag.- nes'ium, ...'F,roh iv the; standpoint. of fuel. economy, fuel-firedcr bles are, muchless efficient than electric furnaces. As shown in Tables III and IV, the .treatment alloys? are made from about 50 to 85% of ferr siIiconand-BO to 15 f,master al1oy. Sincelbyl ourmethod the ferrosilicon con.- stitutes ,a large percent of the total weight. of the treatment alloys. and sincethe ferrosilicon can be made inielectric furnaces having'highzcur rent 'efficiency,. tlie heating cost of making alloys according to 'ourfm'ethodis greatly. reducedas compared with prior methods in Whichthe entire weight of, the ingredients. used in making the tre "tmentfalloyQwaS .riecessarilyv melted in .covcrucibles in.'

, .ing. in,heating costyisinadditio'n o tli'e savingsefiect'ed because of lojwer losses Qrmagnesium. r

Theinyentionisnot. limited: to. .the 7 preier-red em pu mms whi h havepeen. given merely tor purge-$ .04 lust fat may beotherwise eme- 150d. .01. nracticedwithin.thscope.oftherollovw ing claims.

1. The; method of making an alloy containing magnesiumcopper, silicon and iron, which comprises; alloying magnesiu rn with copper and siliconto form an alloy containing magnesium,

copper and silicon and having. amelting point .magnesium copper, silicon and iron,;which comprises; alloyingmagnesium-W-ith copper and silicon to form an alloycontaining from to 55% magnesium from 12'to 50% copper and from 4' to 6.0% silicon, and having amelting .point higher than the melting point of magnesium, andthere after alloying said alloy with ferrosilicon. I :3. The method of-making an alloy containing nagnesium,, copper, silicon and iron, which comprises alloying. magnesiumwith copper and sili-,

.con to form an alloy containing from 10'to magnesium from 1 2,130 copper and from 10 to 40% silicon and having; amelting point higher than. the melting point of magnesium, and thereafter. alloyingsaid alloy withlferrosilicona g 4. Themethod of making i an alloy containing magnesium, copper; silicon and iron; which comprises alloying magnesium with copper, silicon, and. a. substantialamount.butlessthan 20% of iron! toiorm an alloy. containing. magnesium, coppen. silicon. and iron and" having a melting pointhigher. than..the. .melting point voi magnsium, and thereaft'erfalloyin'g said alloy with fer-rosilicon V h 5. The. method. of making. an alloy containing magnesium, ..copper,.silico11 and iron, which comprises: alloying magnesium with. copper, silicon, and irom il to 15%: of iron to' form analloy, containing. magnesium, co'pp'er, silicon and iron. and haying a-melting. point higher than the melt.- ing poihtof, magnesium, andtliereafter. alloying said alloy with ferrosilicon.

. The ifnethodxof. making an. alloy containing rnagnesium c,opper and. silicon; which comprises alloying ;copper and. silicon toform a coppersi lioon alloy, alloying,;copper andmagnesium to fer-pita copper-magnesium. alloy, and alloying Said 9 l.-.J:.'

I I h method of making, an alloy containing magnesium, copper and silicon, which. comprises alloying copperi and: siliconv toform .a copper- .silicon alloyg alloymg. copper and magnesium to form.- a.coppezi magnesium alloy, and=adding said copper-silic n alloy: to amoltenlbathof said? copper-magnesium alloy.

a. The'method of :making. an alloy. containing magnesium copper. and.' silicon, which. comprises melting ,a;m-i1ture.of-; copper and. silicon. in such proportions that. the, vresulting copper-silicon alloy has a melting,poinhsubstantially, lower than the melting point of copper, melting a mixture of magnesium and copper-in such proportions that thezresvulting.magnesium-copperalloy. has amelting point substantially lower than the melting point of magnesium, and alloying said alloys together.

9. The method of making an alloy containing magnesium, copper and silicon, which comprises melting a mixture of copper and silicon in substantially eutectic proportions to form a coppersilicon alloy, melting a mixture of magnesium and copper in substantially eutectic proportions to form a magnesium-copper alloy, and alloying said alloys together.

10. The method of making an alloy containing magnesium, copper, silicon and iron, which comprises melting a mixture of copper and silicon in such proportions that the resulting copper-silicon alloy has a melting point substantially lower than the melting point of copper, melting a mixture of magnesium and copper in such proportions that the resulting magnesium-copper alloy has a melting point substantially lower than the melting point of magnesium, alloying said alloys together to form a master alloy containing magnesium, copper and silicon, and alloying said "master alloy with ferrosilicon.

11. The method of making an alloy containing magnesium, copper, silicon and iron, which comprises alloying copper and ferrosilicon to form a copper-silicon-iron alloy, alloying copper and magnesium to form a copper-magnesium alloy, and alloying said alloys together.

12. The method of making an alloy containing magnesium, copper, silicon and iron, which comprises alloying copper and ferrosilicon in such proportions that the resulting copper-siliconiron alloy has a melting point substantially lower than the melting point of copper, alloying copper and magnesium in such proportions that the resulting copper-magnesium alloy has a melting point substantially lower than the melting point of magnesium, and alloying said alloys together.

13. The method of making an iron-rich alloy containing magnesium, copper, silicon and iron, which comprises melting a mixture of copper and ferrosilicon, in substantially eutectic proportions to form a copper-rich silicon-iron alloy, melting a mixture of magnesium and copper in substantially eutectic proportions to form a magnesiumrich copper alloy, dissolving the copper-rich alloy in the molten magnesium-rich alloy, dissolving copper in molten substantially eutectic ferrosilicon to form an iron-rich silicon-copper alloy, and mixing the two molten alloys in the desired proportions to form an iron-rich quaternary alloy of iron-silicon-copper-magnesium.

HOLBERT E. DUNN. JEROME STRAUSS.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,792,944 Vaders Feb. 17, 1931 2,197,393 Hensel et al Apr. 16, 1940 2,241,575 Barlow May 13, 1941 2,555,014 Strauss May 29, 1951 2,603,563 Crome July 15, 1952 

1. THE METHOD OF MAKING AN ALLOY CONTAINING MAGNESIUM, COPPER, SILICON AND IRON, WHICH COMPRISES ALLOYING MAGNEISUM WITH COPPER AND SILICON TO FORM AN ALLOY CONTAINING MAGNESIUM, COPPER AND SILICON AND HAVING A MELTING POINT HIGHER THAN THE MELTING POINT OF MAGNESIUM, AND THEREAFTER ALLOYING SAID ALLOY WITH FERROSILICON. 